Occurrence of leaf blight of cocoyam (Colocasia esculenta) caused by Phytophthora colocasiae in Jos East L.G.A, Plateau State, Nigeria

Abstract

Production of cocoyam (Colocasia esculenta) in Nigeria has declined in the last few years due to several constraints including poor yield of local cultivars worsened by the spread of Taro Leaf Blight (TLB). Accurate identification and control of the causative pathogen responsible for TLB is a promising option to reduce disease incidence and increase the yield of cocoyam. This study sought to profile occurrence and identity of fungi associated with TLB in Jos East LGA of Plateau State, Nigeria. Eleven farms were surveyed for disease incidence and sampling of infected leaves carried out. Katton Rikkos (Lamingo road) farm had the highest disease incidence of 70% while Koreme and Rifar farms recorded the least (20%). Pathogenicity tests of all isolates showed no visible symptoms four weeks after inoculation. However, Phytopthora spp., used as a positive control showed symptoms of a water-soaked lesion on the leaves three weeks post inoculation. This was followed by a dark brown fleck on the leaves four weeks after inoculation consistent with observed field symptoms in cocoyam. Re-isolation of the isolates confirmed that Phytophthora colocasiae was the potential causal agent of TLB. Further characterization of this pathogen using molecular methods will help in informing appropriate control measures for managing the disease, to increase yield production of cocoyam. Keywords: Taro leaf blight, yield, Phytopthora spp., water soaked lesion, cocoyam